Coatings for cutting tools

- KENNAMETAL INC.

In one aspect, cutting tools are described having coatings adhered thereto which, in some embodiments, can demonstrate desirable wear resistance and increased cutting lifetimes. A coated cutting tool, in some embodiments, comprises a substrate and a coating adhered to the substrate, the coating comprising at least one Zr doped layer deposited by chemical vapor deposition comprising ZrAl2O3.

Skip to: Description  ·  Claims  ·  References Cited  · Patent History  ·  Patent History
Description
RELATED APPLICATION DATA

The present application claims priority pursuant to 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/804,077 filed Mar. 21, 2013, which is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to coatings for cutting tools.

BACKGROUND

Cutting tools, including cemented carbide cutting tools, have been used in both coated and uncoated conditions for machining various metals and alloys. In order to increase cutting tool wear resistance, performance and lifetime, one or more layers of refractory material have been applied to cutting tool surfaces. TiC, TiCN, TiN and/or Al2O3, for example, have been applied to cemented carbide substrates by chemical vapor deposition (CVD) and by physical vapor deposition (PVD). While effective in inhibiting wear and extending tool lifetime in a variety of applications, refractory coatings based on single or multi-layer constructions of the foregoing refractory materials have increasingly reached their performance limits, thereby calling for the development of new coating architectures for cutting tools.

In an effort to increase performance, some have tried to modify Al2O3. DE2736982 to Hillnhagen describes a ceramic matrix (e.g. alumina), into which a further material (e.g. ZrO2) is stored and the stored material has clearly distinct coefficients of thermal expansion producing a coating with very fine micro-cracks.

U.S. Pat. No. 4,702,970 to Sarin et al. and U.S. Pat. No. 4,749,629 to Sarin et al. describe a hard ceramic substrate coated with a ceramic coating having at least two phases. The first phase is a continuous oxide matrix layer of alumina, zirconia, or yttria. At least one discontinuous second or additional phase of oxides of aluminum, zirconium, or yttrium, or solid solutions thereof, is dispersed as discrete particles within the matrix layer. The additional phase material is different from the matrix material.

In Russell, W. C., Strandberg, C., “Wear Characteristics and Performance of Alumina-Zirconia CVD Coatings”, Int. J. of Refractory Metals & Hard Materials, 14 (1996) 51-58, the authors describe using various doped amounts of ZrO2 within an alumina matrix. Further, this article discloses a Ti layer adjacent the substrate followed by a pure alumina layer for adhesion followed by an Al2O3/ZrO2 coating.

U.S. Pat. No. 7,276,301 to Tsushima et al. discloses an α-type (Al,Zr)2O3 layer with a TiOy upper layer. The (Al,Zr)2O3 is deposited having a β-type crystal structure. Post coat heat treatment is described as a method of converting the (Al,Zr)2O3 an α-type crystal structure.

U.S. Pat. No. 7,597,511 to Tomita et al. discloses an aluminum oxide layer with α-type crystal structure and containing Zr. The Zr containing coating is claimed to have a particular crystallographic orientation where a defined Σ3 value is greater than 60%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photomicrograph of a section of a coated cutting insert demonstrating layers of the coating architecture according to one embodiment described herein.

FIG. 2 illustrates a substrate of a coated cutting tool according to one embodiment described herein.

FIG. 3 is an a high angle annual dark field image of a section of ZrAl2O3 produced by a scanning transmission microscopy, hereinafter STEM HAADF. The selected areas differed by composition via x-ray energy dispersive spectrum analysis according to one embodiment described herein.

FIG. 4 illustrates Energy Dispersive X-ray (EDS) spectrographs of the area 1 and area 2 from the image of FIG. 3.

FIG. 5 is an optical image of section of ZrAl2O3 produced according to one embodiment described herein.

 DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by reference to the following detailed description and examples and their previous and following descriptions. Elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

In one aspect, cutting tools are described having coatings adhered thereto which, in some embodiments, can demonstrate desirable wear resistance and increased cutting lifetimes. A coated cutting tool, in some embodiments, comprises a substrate and a coating adhered to the substrate, the coating comprising at least one Zr doped layer deposited by chemical vapor deposition comprising ZrAl2O3. In some embodiments, zirconium is present in a polycrystalline ZrAl2O3 layer in an amount selected from Table XI.

TABLE XI Zr of Polycrystalline ZrAl2O3 Layer Zr Content (wt. %) 0.01-5  0.1-4 0.15-3  0.2-2

In being a dopant, zirconium can be incorporated into the lattice of an Al2O3 phase. In such embodiments, zirconium does not form oxide phase(s) separate from the Al2O3 phase.

Turning now to specific components, a coated cutting tool described herein comprises a substrate. Substrates of coated cutting tools can comprise any material not inconsistent with the objectives of the present invention. In some embodiments, a substrate comprises cemented carbide, carbide, ceramic, cermet, steel, PCD, PcBN or a combination of those listed.

A cemented carbide substrate, in some embodiments, comprises tungsten carbide (WC). WC can be present in a substrate in an amount of at least about 70 weight percent. In some embodiments, WC is present in a substrate in an amount of at least about 80 weight percent or in an amount of at least about 85 weight percent. Additionally, metallic binder of a cemented carbide substrate can comprise cobalt or cobalt alloy. Cobalt, for example, can be present in a cemented carbide substrate in an amount ranging from about 3 weight percent to about 15 weight percent. In some embodiments, cobalt is present in a cemented carbide substrate in an amount ranging from about 5 weight percent to about 12 weight percent or from about 6 weight percent to about 10 weight percent. Further, a cemented carbide substrate may exhibit a zone of binder enrichment beginning at and extending inwardly from the surface of the substrate.

A cemented carbide substrate can also comprise one or more additives such as, for example, one or more of the following elements and/or their compounds: titanium, niobium, vanadium, tantalum, chromium, zirconium and/or hafnium. In some embodiments, titanium, niobium, vanadium, tantalum, chromium, zirconium and/or hafnium form solid solution carbides with the WC in the substrate. The substrate, in some embodiments, comprises one or more solid solution carbides in an amount ranging from about 0.1 weight percent to about 5 weight percent. Additionally, a cemented carbide substrate can comprise nitrogen.

In some embodiments, a substrate of a coated cutting tool described herein comprises one or more cutting edges formed at the juncture of a rake face and flank faces of the substrate. In other embodiments, a substrate of a coated cutting tool is an insert, drill bit, saw blade or other cutting apparatus.

FIG. 1 is photomicrograph of a section of a coated cutting insert demonstrating layers of the coating architecture according to one embodiment described herein. FIG. 2 illustrates a coated cutting insert according to the embodiment shown in FIG. 1. The cutting insert of FIGS. 1 and 2 comprises a substrate 1 of cemented WC. The substrate 1 is coated with multilayer coating. Beginning from the substrate and progressing outward the coating comprises an inner layer 2 of TiN, a MT TiCN layer 3, a TiCN layer 4, a ZrAl2O3 layer 5, a penultimate TiCN layer 6 and an outer TiN layer 7.

FIG. 3 is a HAADF image of a section of a ZrAl2O3 produced by STEM. The selected areas differed by composition via x-ray energy dispersive spectrum analysis according to one embodiment described herein. Area 1 of FIG. 3 highlights a section of a single grain of the ZrAl2O3 coating in which no Zr is present. Area 2 highlights a second area of the same grain in which Zr can be detected. FIG. 4 illustrates Energy Dispersive X-ray (EDS) spectrographs of the Area 1 and Area 2 from FIG. 3. The EDS confirm the presence of Zr in Area 2 and absence of Zr in Area 1. This variable doping has shown be advantageous in certain metalcutting conditions.

FIG. 5 is an optical image of section of ZrAl2O3 produced according to one embodiment described herein. In FIG. 5 a ZrAl2O3 coating is shown. Doped and undoped regions of the coating are indicated.

Further, a polycrystalline ZrAl2O3 layer of a coating described herein can have any thickness not inconsistent with the objectives of the present invention. In some embodiments, a ZrAl2O3 layer has a thickness selected from Table XII.

TABLE XII ZrAl2O3 Layer Thickness (μm) ZrAl2O3 Layer Thickness (μm) 0.5-15   1-12 1.5-10 2.5-8 

A ZrAl2O3 layer can be deposited directly on the cutting tool substrate surface. Alternatively, a coating described herein can further comprise one or more inner layers between the ZrAl2O3 layer and the substrate. One or more inner layers, in some embodiments, comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements selected from the group consisting of non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table. In some embodiments, one or more inner layers between the substrate and ZrAl2O3 layer comprise a carbide, nitride, carbonitride, oxide or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table. For example, one or more inner layers are selected from the group consisting of titanium nitride, titanium carbonitride, titanium carbide, titanium oxide, zirconium oxide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride and alumina and mixtures thereof.

Inner layers of coatings described herein can have any thickness not inconsistent with the objectives of the present invention. An inner layer of a coating can have a thickness ranging from 0.5 μm to 25 μm. In some embodiments, thickness of an inner layer is selected according to the position of the inner layer in the coating. An inner layer deposited directly on a surface of the substrate as an initial layer of the coating, for example, can have a thickness ranging from 0.5 to 2.5 μm. An inner layer deposited over the initial layer, such as a TiCN layer, can have a thickness ranging from 2 μm to 20 μm. Further, an inner layer on which a ZrAl2O3 layer described herein is deposited, such as a layer comprising alumina, can have a thickness ranging from 1 to 6 μm.

In some embodiments, a ZrAl2O3 layer described herein is the outermost layer of the coating. Alternatively, a coating described herein can comprise one or more outer layers over the ZrAl2O3 layer. One or more outer layers, in some embodiments, comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements selected from the group consisting of non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table. In some embodiments, one or more outer layers over the ZrAl2O3 layer comprise a nitride, carbonitride, oxide or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table. For example, one or more outer layers are selected from the group consisting of titanium nitride, titanium carbonitride, titanium carbide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride, titanium oxycarbonitride, zirconium oxycarbonitride, hafnium oxycarbonitride and alumina and mixtures thereof.

Outer layers of coatings described herein can have any thickness not inconsistent with the objectives of the present invention. An outer layer of a coating, in some embodiments, can have a thickness ranging from 0.5 μm to 5 μm.

Additionally, in some embodiments, a coating described herein can comprise one or more bonding layers. A bonding layer can demonstrate various positions in the coating. In some embodiments, a bonding layer is disposed between two inner layers of the coating, such as between a titanium nitride or titanium carbonitride inner layer and an inner layer comprising alumina. A bonding layer can also be disposed between an inner layer and a ZrAl2O3 layer described herein. Further, a bonding layer can be disposed between a ZrAl2O3 layer and an outer layer of the coating. In some embodiments, bonding layers are used to increase adhesion between layers of the coating and/or nucleate the desired morphology of a coating layer deposited on the bonding layer. A bonding layer, in some embodiments, is of the formula M(OxCyNz), wherein M is a metal selected from the group consisting of metallic elements of Groups IVB, VB and VIB of the Periodic Table and x≧0, y≧0 and z≧0 wherein x+y+z=1. For example, in one embodiment, a bonding layer of TiC is employed between an inner layer of TiCN and an inner layer comprising alumina.

A bonding layer of the formula M(OxCyNz) can have any thickness not inconsistent with the objectives of the present invention. In some embodiments, a M(OxCyNz) layer has a thickness of about 0.5 μm. Moreover, a M(OxCyNz) layer can have a thickness ranging from 0.5 μm to 5 μm.

A coating adhered to a substrate can have any architecture of ZrAl2O3 layer, inner layer(s) and/or outer layer(s) described herein. In some embodiments, a coating described herein has an architecture selected from Table VII.

In some embodiments, a coating described herein has a nanoindentation hardness of 2866. The load is about 80 mN with penetration depth of 0.20 μm in 15 s. The hardness is 2866 for certain embodiments described herein.

Additionally, a coating described herein can demonstrate a critical load (Lc) up to about 90 N. Lc values for coatings described herein were determined according to ASTM C1624-05—Standard Test for Adhesion Strength by Quantitative Single Point Scratch Testing wherein a progressive loading of 10 N was used. A coating, for example, can exhibit a Lc value of 60 to 90 N.

In some embodiments the coatings may be post coat blasted. Post coat blasting can be administered in any desired manner. In some embodiments, post coat blasting comprises shot blasting or pressure blasting. Pressure blasting can be administered in a variety of forms including compressed air blasting, wet compressed air blasting, pressurized liquid blasting, wet blasting, pressurized liquid blasting and steam blasting.

In one embodiment, for example, post coat treatment of a coating described herein can be administered by dry blasting the coating with alumina and/or ceramic particles. Alternatively, the coating can be wet blasted using a slurry of alumina and/or ceramic particles in water at a concentration of 5 volume percent to 35 volume percent. Alumina and/or ceramic particles of post-coat blasting techniques described herein can have a size distribution of 60 μm to 120 μm. Additionally, blasting pressures can range from 2 bar to 3 bar for a time period of 1 to 15 seconds, wherein the blast nozzle is 2 to 8 inches from the coating surface being blasted. Further, angle of impingement of the alumina and/or ceramic particles can be chosen to range from 45 degrees to 90 degrees.

In another aspect, methods of making coated cutting tools are described herein. A method of making a coated cutting tool, in some embodiments, comprises providing a substrate and depositing over the substrate by chemical vapor deposition at least one ZrAl2O3 layer of a coating, the ZrAl2O3 layer comprising at least one Zr doped region and one undoped region.

Turning now to specific steps, a method described herein comprises providing a substrate. A substrate can comprise any substrate recited in Section I hereinabove. In some embodiments, for example, a substrate is cemented carbide, such as cemented tungsten carbide described in Section I herein. Moreover, a polycrystalline ZrAl2O3 layer deposited according to methods described herein can have any construction, compositional parameters and/or properties described in Section I herein for a ZrAl2O3 layer.

In a method described herein, a ZrAl2O3 layer can be deposited from a gaseous mixture comprising an aluminum source, oxygen source, nitrogen source and source for the zirconium. In some embodiments, for example, the aluminum source is AlCl3, and the zirconium source is a ZrCl4. In one embodiment a ZrAl2O3 layer is made by alternating Cycle A and Cycle B according to the CVD processing parameters of Table I.

TABLE I Cycle A Cycle B Cycle A Temp.  950-1010  950-1010  950-1010 (° C.) Press. 60-80 60-80 60-80 (mbar) Time 20-90 20-90 20-90 (min.) H2 balance balance balance AlCl3 1.5-3 vol. %   1.5-3 vol. % 1.5-3 vol. %   ZrCl4 — 0.2-1 vol. % — CO2 3-6 vol. %   3-6 vol. % 3-6 vol. % HCl 1-3 vol. %   1-3 vol. % 1-3 vol. % H2S 0.15-0.6 vol. %   0.15-0.6 vol. %  0.15-0.6 vol. %   Ar —    1-2% —

In another embodiment a ZrAl2O3 coating is made according to the CVD processing parameters provided in Table II. The embodiment described in Table II provides a Zr doping gradient in the Zr doped section of the ZrAl2O3 coating. Cycles C-I may be shorten and repeated to induce alternating intragranular doped and undoped regions.

TABLE II Cycle C Cycle D Cycle E Cycle F Cycle G Cycle H Cycle I Temp. ( ° C.)  950-1010  950-1010  950-1010  950-1010  950-1010  950-1010  950-1010 Press. (mbar) 60-80 60-80 60-80 60-80 60-80 60-80 60-80 Time (min.) 20-90 20-90 20-90 H2 balance balance balance balance balance balance balance AlCl3 (vol. %) 1.5-3  1.5-3  1.5-3  1.5-3  1.5-3  1.5-3  1.5-3  ZrCl4 (vol. %) — 0.10-0.15 0.18-0.21 0.24-0.26 0.18-0.21 0.10-0.15 — CO2 (vol. %) 3-6 3-6 3-6 3-6 3-6 3-6 3-6 HCl (vol. %) 1-3 1-3 1-3 1-3 1-3 1-3 1-3 H2S (vol. %) 0.15-0.6  0.15-0.6  0.15-0.6  0.15-0.6  0.15-0.6  0.15-0.6  0.15-0.6  Ar (vol %) — 1-2 1-2 1-2 1-2 1-2 —

In another embodiment a ZrAl2O3 coating is made according to the CVD processing parameters provided in Table III. The embodiment described in Table III provides a Zr doping gradient in the Zr doped section of the ZrAl2O3 coating. Cycles J-P may be shortened and repeated to induce alternating intragranular doped and undoped regions.

TABLE III Cycle J Cycle K Cycle L Cycle M Cycle N Cycle O Cycle P Temp. ( ° C.) 990-1000 990 990 990 990 990 990-1000 Press. (mbar) 75 75 75 75 75 75 75 Time (min.) 20-90  20-90 20-90  H2 balance balance balance balance balance balance balance AlCl3 (vol. %) 1.96 1.84 1.84 1.83 1.84 1.84 1.96 ZrCl4 (vol. %) — 0.4 0.61 0.80 0.61 0.4 — CO2 (vol. %) 3.44 4.2 4.19 4.18 4.19 4.2 3.44 HCl (vol. %) 1.38 1.29 1.29 1.29 1.29 1.29 1.38 H2S (vol. %) 0.26 0.24 0.24 0.24 0.24 0.24 0.26 Ar (vol %) — 4.84 4.83 4.82 4.83 4.84 —

In another embodiment a ZrAl2O3 coating is made according to the CVD processing parameters provided in Table IV. The embodiment described in Table IV provides a Zr doping gradient in the Zr doped section of the ZrAl2O3 coating. Cycles Q-S may be shortened and repeated to induce alternating intragranular doped and undoped regions.

TABLE IV Cycle Q Cycle R Cycle S Temp. (° C.)  990-1000 990 990-1000 Press. (mbar) 75    75 75    Time (min.) 20-90 20-90 20-90 H2 balance balance balance AlCl3 (vol. %) 1.96 1.65 1.96 ZrCl4 (vol. %) — 0.72 — CO2 (vol. %) 3.44 3.76 3.44 HCl (vol. %) 1.38 1.16 1.38 H2S (vol. %) 0.26 0.22 0.26 Ar (vol %) — 14.45 —

In another embodiment a ZrAl2O3 coating is made according to the CVD processing parameters provided in Table V. The embodiment described in Table V provides a Zr doping gradient in the Zr doped section of the ZrAl2O3 coating. Cycles T-V may be shortened and repeated to induce alternating intragranular doped and undoped regions.

TABLE V Cycle T Cycle U Cycle V Temp. (° C.)  990-1000 990  990-1000 Press. (mbar) 75    75 75    Time (min.) 20-90 20-90 20-90 H2 balance balance balance AlCl3 (vol. %) 1.96 1.44 1.96 ZrCl4 (vol. %) — 0.63 — CO2 (vol. %) 3.44 3.28 3.44 HCl (vol. %) 1.38 1.01 1.38 H2S (vol. %) 0.26 0.19 0.26 Ar (vol %) — 24.26 —

A ZrAl2O3 layer, in some embodiments, is deposited directly on a surface of the substrate. Alternatively, a ZrAl2O3 layer is deposited on an inner layer of the coating. An inner layer of the coating can have any construction, compositional parameters and/or properties recited in Section I hereinabove for an inner layer. An inner layer can comprise one or more metallic elements selected from the group consisting of aluminum and one or more metallic elements of Groups IVB, VB, and VIB of the Periodic Table and one or more non-metallic elements selected from the group consisting of non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table. In some embodiments, an inner layer is a carbide, nitride, carbonitride, oxide or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table. An inner layer over which a ZrAl2O3 layer is deposited, for example, can be selected from the group consisting of titanium nitride, titanium carbide, titanium carbonitride, titanium oxide, zirconium oxide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride and alumina and mixtures thereof. In one embodiment, for example, an inner layer comprises a mixture of alumina, zirconium oxide and titanium oxide (Al2O3/ZrO2/TiOx).

As with the ZrAl2O3 layer, inner layer(s) of a coating described herein can be deposited by CVD. In some embodiments, an inner layer of the coating, such as a TiCN layer, is deposited by medium-temperature (MT) CVD.

Further, methods described herein can also comprise depositing over the ZrAl2O3 layer one or more outer layers. Outer layer(s) of a coating described herein, in some embodiments, are deposited by CVD. An outer layer of the coating can have any construction, compositional parameters and/or properties recited in Section I hereinabove for an outer layer. An outer layer can comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements selected from the group consisting of non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table. In some embodiments, one or more outer layers over the ZrAl2O3 layer comprise a nitride, carbonitride, oxide or boride of one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table. For example, one or more outer layers are selected from the group consisting of titanium nitride, titanium carbonitride, titanium carbide, zirconium nitride, zirconium carbonitride, hafnium nitride, hafnium carbonitride, titanium oxycarbonitride, hafnium oxycarbonitride, zirconium oxycarbonitride and alumina and mixtures thereof.

Coatings of cutting tools described herein can be subjected to post-coat treatments. Coatings, for example, can be blasted with various wet and/or dry particle compositions. Post coat blasting can be administered in any desired manner. In some embodiments, post coat blasting comprises shot blasting or pressure blasting. Pressure blasting can be administered in a variety of forms including compressed air blasting, wet compressed air blasting, pressurized liquid blasting, wet blasting, pressurized liquid blasting and steam blasting. Wet blasting, for example, is accomplished using a slurry of inorganic and/or ceramic particles, such as alumina, and water. The alumina particle slurry can be pneumatically projected at a surface of the coated cutting tool body to impinge on the surface of the coating. The alumina particles can generally range in size between about 20 μm and about 100 μm.

Blasting parameters include pressure, angle of impingement, distance to the part surface and duration. In some embodiments, angle of impingement can range from about 45 degrees to about 90 degrees, i.e., the particles impinge the coating surface at an angle ranging from about 45 degrees to about 90 degrees. Suitable pressures can range from 30-55 pounds per square inch (psi) at a distance to the coated surface of 1-6 inches. Further, duration of the blasting can generally range from 1-10 seconds or longer. Blasting can be generally administered over the surface area of the coating or can be applied to select locations such as in a workpiece contact area of the cutting tool. A workpiece contact area can be a honed region of the cutting tool.

In other embodiments, a coating is subjected to a polishing post-coat treatment. Polishing can be administered with paste of appropriate diamond or ceramic grit size. Grit size of the paste, in some embodiments, ranges from 1 μm to 10 μm. In one embodiment, a 5-10 μm diamond grit paste is used to polish the coating. Further, grit paste can be applied to the CVD coating by any apparatus not inconsistent with the objectives of the present invention, such as brushes. In one embodiment, for example, a flat brush is used to apply grit paste to the CVD coating in a workpiece contact area of the cutting tool.

A coating described herein can be blasted or polished for a time period sufficient to achieve a desired surface roughness (Ra) and/or other parameters such as reducing residual tensile stress in the coating. In some embodiments, a coating subjected to post-coat treatment has a surface roughness (Ra) selected from Table VI.

TABLE VI Post-Coat Surface Roughness (Ra) Polished Coating Surface Roughness (Ra) - nm ≦0500 ≦250 <200 10-250 50-175 25-150

Coating surface roughness can be determined by optical profilometry using WYKO® NT-Series Optical Profilers commercially available from Veeco Instruments, Inc. of Plainview, N.Y.

Further, a post-coat treatment, in some embodiments, does not remove one or more outer layers of the coating. In some embodiments, for example, a post-coat treatment does not remove an outer layer of TiN and/or TiCN. Alternatively, a post-coat treatment can remove or partially remove one or more outer layers, such as TiN and/or TiCN.

By alternating Zr doped and undoped regions of a ZrAl2O3 coating and by providing a Zr gradient in the Zr doped regions of the ZrAl2O3 coating, the inventors have improved the material properties and wear resistance of the ZrAl2O3 coatings. The ZrAl2O3 coatings are believed to have an increased micro-hardness due to a grain size decrease along with enhanced local boding along grain boundaries due to Zr atoms segregating to localized regions along the grain boundaries. Sequential doped and undoped regions also are believed to affect the grain growth kinetics, defect levels and interfacial structure compared to Al2O3 thin films.

These and other embodiments are further illustrated in the following non-limiting examples.

EXAMPLE 1 Coated Cutting Tool Body

Coated cutting tools 1 and 2 described herein were produced by placing cemented tungsten carbide (WC) cutting insert substrates [ANSI standard geometry CNMG432RN] into an axial flow hot-wall CVD reactor. The cutting inserts each comprised 7 wt. % cobalt binder with the balance WC grains of size 1 to 5 μm. A coating having an architecture provided in Table VII was deposited on the cemented WC cutting inserts according to the CVD process parameters provided in Table II. ZrCl4 was presented in the CVD gas mixture in gradient steps to provide a polycrystalline ZrAl2O3 layer having an intra-layer compositional gradient of Al2O3 stages alternating with a gradient ZrAl2O3 stage.

TABLE VII CVD Coating Architecture Substrate CVD Coating Architecture WC—Co TiN*—TiCN(MT)—TiCN(HT)/TiOCN—ZrAl2O3—TiN/ TiCN *Innermost layer adjacent to the substrate

The multilayered coatings of cutting inserts 1 and 2 comprising the polycrystalline ZrAl2O3 layer exhibited the properties provided in Table VIII.

TABLE VIII Properties of CVD Coating Coating Layers Thickness (μm) TiN* 0.3-0.7 TiCN(MT) 8.5-9   TiCN(HT)/TiOCN 0.8-1.2 ZrAl2O3 6.8-7.2 TiN/TiCN 1.3-1.7 *Coating Layer adjacent to WC—Co Substrate

FIG. 1 is a cross-sectional SEM image of a coated cutting insert of this Example 1 demonstrating layers of the coating architecture. Further, cutting insert 1 was subjected to dry polishing with diamond paste and cutting insert 2 was subjected wet-blasting with alumina grit as a post coat treatment.

EXAMPLE 2 Metal Cutting Testing

Coated cutting inserts (1-2) of Example 1 and Comparative coating insert 3 were subjected to continuous turning testing of 1045 steel according to the parameters below. Comparative cutting insert 3 displayed a coating architecture and properties set forth in Table IX. Comparative cutting insert 3 employed a WC-Co substrate of substantially similar composition as Example 1 and an ANSI standard geometry CNMG432RN. Comparative cutting insert 3 was subjected to a wet blasting with alumina grit as a post coat treatment.

TABLE IX Comparative cutting insert 3 Coating Layers Thickness (μm) TiN* 0.1-0.5 TiCN(MT) 7.0-9.0 TiCN(HT)/TiOCN 0.8-1.3 Al2O3 7.1-8.5 TiN/TiCN removed *Coating Layer adjacent to WC—Co Substrate

Coated cutting inserts 1 and 2 of Example 1 and Comparative coating insert 3 were subjected to continuous turning testing as follows:
  • Workpiece—1045 Steel
  • Speed—1000 sfm (304.8 m/min)
  • Feed Rate—0.012 ipr (0.3048 mm/min)
  • Depth of Cut—0.08 inch (0.08 mm)
  • Lead Angle: −5°
    End of Life was registered by one or more failure modes of:
  • Uniform Wear (UW) of 0.012 inches
  • Max Wear (MW) of 0.012 inches
  • Nose Wear (NW) of 0.012 inches
  • Depth of Cut Notch Wear (DOCN) Of 0.012 inches
  • Trailing Edge Wear (TW) of 0.012 inches
    Two cutting inserts were tested for each coating architecture (1-3) providing repetition 1 and 2 data as well as mean cutting lifetime. The results of the continuous turning testing are provided in Table X.

TABLE X Continuous Turning Testing Results Repetition 1 Repetition 2 Cutting Lifetime Lifetime Mean Cutting Insert (minutes) (minutes) Lifetime (minutes) 1 21.3 24.5 22.9 2 23.1 23.1 23.1 3 20.4 19.9 20.2

As provided in Table X, coated cutting tools 1 and 2 demonstrated the better mean cutting lifetime. Coating cutting tools 1 and 2 demonstrated about 14.0% improvement in cutting lifetime than coated cutting tool 3.

Various embodiments of the invention have been described in fulfillment of the various objects of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A coated cutting tool comprising:

a substrate; and
a coating adhered to the substrate comprising a polycrystalline layer of ZrAl2O3, the polycrystalline ZrAl2O3 layer having an intra-layer compositional gradient formed of an Al2O3 region transitioning to a ZrAl2O3 region along thickness of the polycrystalline layer.

2. The coated cutting tool of claim 1, wherein Al2O3 regions and ZrAl2O3 regions alternate along the thickness of the polycrystalline layer.

3. The coated cutting tool of claim 1, wherein the ZrAl2O3 stage has a zirconium gradient therein.

4. The coated cutting tool of claim 1, wherein an individual grain of the polycrystalline ZrAl2O3 layer displays the compositional gradient formed of the Al2O3 region transitioning to the ZrAl2O3 region.

5. The coated cutting tool of claim 1, wherein zirconium is located in the ZrAl2O3 region adjacent to one or more grain boundaries.

6. The coated cutting tool of claim 1, wherein zirconium is present in the polycrystalline ZrAl2O3 layer in an amount 0.01-2 wt. %.

7. The coated cutting tool of claim 1, wherein the thickness of the polycrystalline ZrAl2O3 layer is 2.5 to 8 μm.

8. The coated cutting tool of claim 1, wherein the coating further comprises one or more base layers between the substrate and the ZrAl2O3 polycrystalline layer.

9. The coated cutting tool of claim 8, wherein a base layer comprises one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table.

10. The coated cutting tool of claim 9, wherein the one or more base layers are selected from the group consisting of TiN, TiCN and TiOCN.

11. The coated cutting tool of claim 1, wherein the coating further comprises one or more outer layers over the polycrystalline ZrAl2O3 layer.

12. The coated cutting tool of claim 11, wherein an outer layer comprises one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table.

13. The coated cutting tool of claim 11, wherein the coating is post-coat blasted with ceramic or inorganic particles.

14. The coated cutting tool of claim 11, wherein the coating is polished.

15. The coated cutting tool of claim 1, wherein the polycrystalline ZrAl2O3 layer is deposited by thermal CVD.

16. The coated cutting tool of claim 1, wherein the substrate comprises cemented tungsten carbide or polycrystalline cubic boron nitride.

17. The coated cutting tool of claim 1, wherein the substrate is an insert, drill bit or saw blade.

18. The coated cutting tool of claim 1, wherein the coating exhibits a critical load (Lc) of 60 to 90 N according to ASTM C1624-05—Standard Test for Adhesion by Quantitative Single Point Scratch Testing.

19. A coated cutting tool comprising:

a substrate; and
a coating adhered to the substrate, the coating comprising a polycrystalline layer of ZrAl2O3 having a zirconium gradient along one or more ZrAl2O3 grains, the gradient formed of an Al2O3 region transitioning to a ZrAl2O3region along a vertical dimension of the one or more ZrAl2O3 grains.

20. The coated cutting tool of claim 19, wherein the ZrAl2O3 region has a zirconium gradient therein.

21. The coated cutting tool of claim 19, wherein Al2O3 regions alternate with ZrAl2O3 regions along the vertical dimension of the one or more ZrAl2O3 grains.

22. The coated cutting tool of claim 19, wherein zirconium is present in the polycrystalline ZrAl2O3 layer in an amount 0.01-5 wt. %.

23. The coated cutting tool of claim 19, wherein the polycrystalline ZrAl2O3 layer has a thickness of 2.5 to 8 μm.

24. The coated cutting tool of claim 19, wherein the coating further comprises one or more base layers between the substrate and the polycrystalline layer of ZrAl2O3.

25. The coated cutting tool of claim 24, wherein a base layer comprises one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table.

26. The coated cutting tool of claim 25, wherein the one or more base layers are selected from the group consisting of TiN, TiCN and TiOCN.

27. The coated cutting tool of claim 19, wherein the coating further comprises one or more outer layers over the polycrystalline TiZrAl2O3 layer.

28. The coated cutting tool of claim 27, wherein an outer layer comprises one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB and VIB of the Periodic Table and one or more non-metallic elements of Groups IIIA, IVA, VA and VIA of the Periodic Table.

29. The coated cutting tool of claim 27, wherein the coating is post-coat blasted with ceramic or inorganic particles.

30. The coated cutting tool of claim 27, wherein the coating is polished.

31. The coated cutting tool of claim 19, wherein the polycrystalline ZrAl2O3 layer is deposited by thermal CVD.

32. The coated cutting tool of claim 19, wherein the substrate comprises cemented tungsten carbide or polycrystalline cubic boron nitride.

33. The coated cutting tool of claim 19, wherein the substrate is an insert, drill bit or saw blade.

34. The coated cutting tool of claim 19, wherein the coating exhibits a critical load (Lc) of 60 to 90 N according to ASTM C1624-05—Standard Test for Adhesion by Quantitative Single Point Scratch Testing.

Referenced Cited
U.S. Patent Documents
4052530 October 4, 1977 Fonzi
4112148 September 5, 1978 Fonzi
4180400 December 25, 1979 Smith et al.
4576836 March 18, 1986 Colmet et al.
4701384 October 20, 1987 Sarin et al.
4702970 October 27, 1987 Sarin et al.
4745010 May 17, 1988 Sarin et al.
4746563 May 24, 1988 Nakano et al.
4749629 June 7, 1988 Sarin et al.
4751109 June 14, 1988 Sarin et al.
4844951 July 4, 1989 Sarin et al.
5310607 May 10, 1994 Schulz et al.
5447804 September 5, 1995 Schulz et al.
5709907 January 20, 1998 Battaglia et al.
5722803 March 3, 1998 Battaglia et al.
5770261 June 23, 1998 Nakamura et al.
5827570 October 27, 1998 Russell
5861210 January 19, 1999 Lenander et al.
5871850 February 16, 1999 Moriguchi et al.
5879823 March 9, 1999 Prizzi et al.
5972495 October 26, 1999 Ishii et al.
5985427 November 16, 1999 Ueda et al.
6156383 December 5, 2000 Ishii et al.
6161990 December 19, 2000 Oles et al.
6183846 February 6, 2001 Moriguchi et al.
6333103 December 25, 2001 Ishii et al.
6426137 July 30, 2002 Oshika et al.
6436519 August 20, 2002 Holzschuh
6599062 July 29, 2003 Oles et al.
6641939 November 4, 2003 Lee et al.
6660371 December 9, 2003 Westphal et al.
6689422 February 10, 2004 Warnes et al.
6713172 March 30, 2004 Ljungberg et al.
6726987 April 27, 2004 Kathrein et al.
6756111 June 29, 2004 Okada et al.
6849132 February 1, 2005 Warnes et al.
6869668 March 22, 2005 Martensson
6902764 June 7, 2005 Ljungberg et al.
7011867 March 14, 2006 Martensson
7090914 August 15, 2006 Yamagata et al.
7094447 August 22, 2006 Ruppi
7163735 January 16, 2007 Ruppi
7241492 July 10, 2007 Kohara et al.
7273665 September 25, 2007 Hayahi et al.
7276301 October 2, 2007 Tsushima et al.
7326461 February 5, 2008 Sottke et al.
7378158 May 27, 2008 Richter et al.
7396581 July 8, 2008 Ruppi
7410707 August 12, 2008 Fukui et al.
7416778 August 26, 2008 Westergren et al.
7442433 October 28, 2008 Honma et al.
7498089 March 3, 2009 Omori et al.
7531212 May 12, 2009 Kohara et al.
7531213 May 12, 2009 Bjormander
7597511 October 6, 2009 Tomita et al.
7597951 October 6, 2009 Bjormander et al.
7597970 October 6, 2009 Fukano et al.
7691496 April 6, 2010 Park et al.
7803464 September 28, 2010 Okada et al.
7820310 October 26, 2010 Bjormander
7901788 March 8, 2011 Warnes et al.
7906230 March 15, 2011 Watanabe et al.
7923101 April 12, 2011 Ruppi
7928028 April 19, 2011 Nawa et al.
7939181 May 10, 2011 Ramm et al.
7967533 June 28, 2011 Omori et al.
7968182 June 28, 2011 Trinh et al.
7972714 July 5, 2011 Okada et al.
8003234 August 23, 2011 Omori et al.
8012611 September 6, 2011 Okada et al.
8025991 September 27, 2011 Schier
8071211 December 6, 2011 Koike et al.
8080312 December 20, 2011 McNerny et al.
8080323 December 20, 2011 Ban et al.
8097332 January 17, 2012 Omori et al.
8119226 February 21, 2012 Reineck et al.
8119227 February 21, 2012 Reineck et al.
8129040 March 6, 2012 Quinto et al.
8152971 April 10, 2012 Quinto et al.
8221838 July 17, 2012 Gates, Jr. et al.
8288019 October 16, 2012 Nagano et al.
20010006724 July 5, 2001 Holzschuh
20020081447 June 27, 2002 Movchan et al.
20020114945 August 22, 2002 Greenberg et al.
20020119017 August 29, 2002 Gates, Jr. et al.
20040224159 November 11, 2004 Oshika et al.
20040241490 December 2, 2004 Finley
20050260454 November 24, 2005 Fang et al.
20060029813 February 9, 2006 Kutilek et al.
20060292390 December 28, 2006 Kassner et al.
20070212895 September 13, 2007 Chua et al.
20070289280 December 20, 2007 Marquardt
20080196318 August 21, 2008 Bost et al.
20100166512 July 1, 2010 Tanibuchi
20100303566 December 2, 2010 Fang et al.
20120003452 January 5, 2012 Tomita et al.
Foreign Patent Documents
102581324 July 2012 CN
2736982 March 1979 DE
0786536 May 2003 EP
1655387 May 2008 EP
56152962 November 1981 JP
57158372 September 1982 JP
5921586 February 1984 JP
5985860 May 1984 JP
0516031 January 1993 JP
4195518 July 1998 JP
4019244 June 2002 JP
2003039207 February 2003 JP
2005205516 August 2005 JP
2006219739 August 2006 JP
4645983 October 2006 JP
2006289556 October 2006 JP
2008019489 January 2008 JP
2008019498 January 2008 JP
4822120 February 2008 JP
5019255 January 2009 JP
5099490 April 2009 JP
5099500 July 2009 JP
2011057529 March 2011 JP
2011127165 June 2011 JP
2011184295 September 2011 JP
2012143825 August 2012 JP
1020060102658 September 2006 KR
02/077312 October 2002 WO
Other references
  • Martensson “Influence of the concetnration of ZrCl4 on the texture, morphology and growth rate of CVD grown alpha-Al2O3 coatings deposited by AlCl3/Zrcl4/H2/Co2/H2S process” Surface & technology 200 (2006) p. 3626-3632.
  • X. Feng et al., “Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres”, Science Magazine, vol. 312, Jun. 9, 2006, pp. 1504-1508.
  • Z. Yu et al., “Atomic-resolution observation of Hf-doped alumina grain boundaries”, SciVerse ScienceDirect, Scripta Materialia 68 (2013) pp. 703-706.
  • N. Shibata et al., “Atomic-scale imaging of individual dopant atoms in a buried interface”, Nature Materials, vol. 8, 2009, pp. 654-658.
  • J. P. Buban et al., “Grain Boundary Strengthening in Alumina by Rare Earth Impurities”, Science Magazine, vol. 311, Jan. 13, 2006, pp. 212-215.
  • Z. Li et al., “Nanodomain formation and distribution in Gd-doped ceria”, SciVerse ScienceDirect, Materials Research Bulletin 47 (2012) pp. 763-767.
  • C. Bjormander, “CVD deposition and characterization of coloured Al2O3/ZrO2 multilayers”, ScienceDirect, Surface & Coatings Technology 201 (2006) pp. 4032-4036.
  • D. Hochauer et al., “Titanium doped CVD alumina coatings”, ScienceDirect, Surface & Coatings Technology 203 (2008) pp. 350-356.
  • W. C. Russell et al., “Wear Characteristics and Performance of Composite Alumina-Zirconia CVD Coatings*”, Int. J. of Refractory Metals & Hard Materials 14 (1996) pp. 51-58.
  • S. Taylor, “Grain Boundary Structure and Solute Segregation in Titanium-Doped Sapphire Bicrystals”, Disseeration, University of California, Berkley, Spring 2002, pp. 1-222.
  • Jul. 7, 2014—PCT—Search—Report—and—Written—Opinion.
  • Kathrein et al., “Doped CVD Al203 Coatings for High Performance Cutting Tools”, Surface & Coatings Technology 163-164 (2001), pp. 181-188.
  • Moltrecht, “Machine Shop Practice”, Industrial Press Inc., New York, New York (1981), pp. 199-204.
  • ASTE Tool Engineers Handbook; McGraw Hill Book Co., New York, New York (1949), pp. 302-315.
  • International Search Report for PCT Application No. PCT/US2014/031358, mailed Jul. 7, 2014, 1 page.
  • International Search Report for PCT Application No. PCT/US2014/031291, mailed Jul. 4, 2014, 1 page.
Patent History
Patent number: 9181620
Type: Grant
Filed: Mar 20, 2014
Date of Patent: Nov 10, 2015
Patent Publication Number: 20140287229
Assignee: KENNAMETAL INC. (Latrobe, PA)
Inventors: Karl Heinz Wendt (Ebermannstadt), Volkmar Sottke (Mulheim), Peter Rudolf Leicht (Latrobe, PA), Yixiong Liu (Greensburg, PA), Mark S. Greenfield (Greensburg, PA), Hartmut Westphal (Dermbach)
Primary Examiner: Archene Turner
Application Number: 14/221,138
Classifications
Current U.S. Class: With Inorganic Material (51/307)
International Classification: C23C 16/06 (20060101); C23C 16/40 (20060101); C23C 16/455 (20060101); C23C 30/00 (20060101);